Liquid seal for wet roof bit

ABSTRACT

Fluid roof bits for mining typically supply high pressure water to a location immediately adjacent the cutting insert of the roof bit to flush debris and cool the cutting insert. The present invention is a drill steel assembly for a wet roof bit that reduces the fluid pressure loss supplied to the roof bit. A drill head body is connected to the drill steel by an intermediate adaptor. The adaptor has a spring loaded button thereon that mates with an opening in the drill head body so that the drill head body can be conveniently snapped onto the drill head assembly. A bushing seal made from a flexible material is clamped between said drill steel adaptor and the drill head body to limit fluid pressure losses.

[0001] This application is a continuation of U. S. ProvisionalApplication No. 60/322,645, filed Sep. 17, 2001.

BACKGROUND OF THE INVENTION

[0002] 1. Field of the Invention

[0003] This invention relates to a method and apparatus for drillingholes in mines for inserting roof bolts so that roof bolts can beinserted and fixed in roof rock faces to prevent their collapse.

[0004] 2. Prior Art

[0005] Procedures utilized for the subterranean mining of coal have beengreatly improved over the past several decades, both from the standpointof operational safety on the part of miners as well as from thestandpoint of their productivity. However, mining practices still areconsidered to be labor intensive, a factor significant in the pricing ofcoal. Additionally, current mining procedures necessarily continue topose severe occupational safety difficulties. While current techniquesof subterranean mining specific to a given strata being worked mayrepresent a variety of technical approaches, the sequence of a givencoal mining operation tends to follow a general pattern wherein machinesof one variety or another work at the face of a seam to extract coalwhich then is conveyed outwardly from the mine. During this extractionprocedure, there is created a progressively expanding subterraneancavern or chamber. As this procedure is carried out, the structuralintegrity of the immediately adjacent portions of the cavern roof orsupporting portions is jeopardized. Consequently, the roof must bebuttressed.

[0006] A variety of techniques have been developed and continue to bedeveloped to achieve roof integrity; however, an important and mostprevalent one of such techniques provides for the utilization of whatare referred to in the art as “roof bolts”. Typically, the procedure forbolting involves first, the carrying out of vertical and predeterminedangular drilling through the roof of a recently mined area. Thisdrilling normally will extend at least through a predetermined width ofstrata. Next, elongate steel bolts are inserted into the bores andanchored therein.

[0007] In the past, rotary drilling and coring tools, as used in miningand construction, have been constructed with hardened drill bit cuttingheads, and traditionally with sintered carbide inserts to prolong theoperative life of the tool. Typical cutting tools may use a single orcontinuous cutting surface or edge, but most frequently employ aplurality of discrete cutting elements or coring bits eithersequentially or angularly arranged on a rotary bit or auger of sometype.

[0008] A principal problem encountered in all of these prior art toolshas been the rapid wear and high cost of replacement along with machinedowntime. Such rapid tool wear and breakage, in part due to higher speedequipment and heavier frictional forces and tensile stress, has ledtoward tool redesign with some larger carbide insert or drilling tipconfigurations—which in some applications has resulted in higher dustlevels and increased potential ignition dangers contrary to miningsafety regulations. Pressurized water supplied to roof bit drillingoperations adjacent to the drill bit has been employed to reduce dustand improve drilling rates.

[0009] Wet carbide drilling in the past utilized the delivery of wateror other flushing fluids at low pressures in the range of 60-80 psi. Theresult of such prior art methods was that a single rotary drill bitusing a sintered carbide insert, such as a roof drill bit of the typeshown in the drawings, should be expected to drill at least one four(4′) foot bore before breaking or wearing out and might drill several ofsuch bores, although in some hard rock formations, two or more prior artcarbide bits might be required to drill a single 4′ bore. As detailed inU.S. Pat. No. 5,303,787, wet drilling increased performance and reduceddust and produced dramatic results even using the traditional methods ofthe prior art. Some comparison tests pertaining to water pressurechanges only have been made in the industry; nine (9) insert rotary roofbits were operating at a conventional water pressure of 80 psi drilled12,420 feet of rock for an average of 1,380 ft./bit. In this comparisontest, eighteen rotary roof bits embodying the same configuration wereoperated in the same mine at water pressures of 300 psi and drilled72,822 feet of rock for an average of 4,056 ft./bit.

[0010] In many instances, certain of the interconnected components ofthe drill steel are lost by virtue of their frictional engagement withinthe bore, which they have formed. For the most part, the drill steelcomponents are interconnected by slideably mating male and femaleconnections, which have no provision for providing tensional coupling topermit forced withdrawal from a bore. Some attempts to alleviate thisdrill steel loss have generally looked to the use of pins, which aredriven through mating bores, which are formed within the female and maleconnections. However, such arrangements are found to be impractical inactual mining practice. The miner, generally operating in a posturesomewhat near to prone, will remain entirely unappreciative ofrequirements for carrying punch and hammer first to insert, then toremove the pins as the drill steel is withdrawn from the bore. Suchremoval within a mine atmosphere is both hazardous and entirelyimpractical from a human engineering standpoint. Snap buttons have beenadopted to simplify assembly of the drill steel and enable a miner toassemble the drill steel together quickly in a convenient manner. Suchsnap on coupling devices, however, are subject to leaking, resulting inundesirable water pressure losses in wet drilling operations.

SUMMARY

[0011] The present invention is addressed to a roof drilling system forsubterranean mining applications improving the efficiency, safety andeconomics of present-day mine securing techniques. Recognizing therealities of the physical requirements levied upon miners carrying outroof drilling operations, the system of the invention provides for aneffective and convenient withdrawal of drill steel immediately followingformation of a roof bore. However, once the drill head is lowered fromthe face of the bore and, consequently, the drill steel assemblage islowered, a simple, push button release maneuver on the part of the minerprovides for full disconnection of the drill steel from the drill headassembly.

[0012] It is an object of the present invention, therefore, to providean improved rotary mining tool characterized by increased wearresistance and tool life; to provide novel methods of rock mining inwhich the tool life is greatly prolonged; to provide methods utilizingsubstantially increased water delivery rates to cool the roof bit andreduce dust, wherein a liquid seal is included in the drill headassembly so that water is communicated adjacent to the roof bit insertwithout substantial leaking or pressure loss.

BRIEF DESCRIPTION OF THE DRAWINGS

[0013]FIG. 1 is a sectional pictorial representation of a miningapparatus used for mining a seam having a roof bit drill for drillingbores.

[0014]FIG. 2 is a cross sectional view of a drill head assembly.

[0015]FIG. 3 is and exploded view of the drill head assembly illustratedin FIG. 2.

[0016]FIG. 4 is a cross-sectional view taken along lines 4-4 in FIG. 3.

[0017]FIG. 5 is another exploded view of the drill head assemblyillustrated in FIG. 2 taken from a line of sight rotated 90 degrees withrespect to the longitudinal axis of the drill head illustrated in FIG.3.

DESCRIPTION OF THE INVENTION

[0018] Referring to FIG. 1, a typical roof-drilling machine is depictedgenerally at 10. Machine 10 is designed such that it operates inconjunction with the relatively low seams of coal now often encounteredin mining operations. For example, the roof of the subterranean cavern12 formed subsequent to the removal of coal from the seam, asrepresented at 14, may be as low as about thirty inches, a height stillof magnitude sufficient to carry out mining operations. In conventionalmining practice, following the extraction of a given quantity of coal orother mined commodity from the seam, extraction and shuttle mechanismsare removed from the recently mined area and drilling machines as at 10are advanced to aid in carrying out necessary roof bolting operations tosecure roof 14. Boom components 16 are operated by a miner and may belowered such that drill head 18 touches the floor of the cavern. In thecourse of providing a vertical bore, the miner inserts the drive-inportion of a starter steel component within the chuck and receivingcavity of drill head 18.

[0019] Starter steel components generally will incorporate a drill bitat their tip and the head 18 rotates the assemblage while being elevatedby boom 16 in a manner defining a consistent vertical drill axisorientation. A driver steel component, as represented at 30 in FIG. 1,is inserted within the receiving cavity of the chuck of drill head 18.To this driver steel component 30 directly or indirectly is attached a“finisher” which serves as a holder for the drill bit for ensuingdrilling operations. Such a finisher component is represented in FIG. 1at 32, while the drill bit head, conventionally formed of carbide, isrepresented at 34.

[0020] For low seam coal, a succession of such drill elongatingmanipulations are required, a predetermined number of middle extensioncomponents, as represented at 36 in FIG. 1, being inserted between thedriver steel component 30 and finisher component 32 to achieve requisitebore height. Of course, the lengths of any of the above componentsselected will depend upon a seam height encountered.

[0021] Upon completion of a bore, the drill steel assembly must beremoved therefrom and the general practice in this regard is to lowerboom 16 and head 18. As the head 18 is lowered, the drive-in portion 38of the driver steel component 30 slides directly outwardly from thereceiving cavity of the rotatable chuck. Grasping the exposed shankportion of the driver steel 30 and subsequent extensions 36 as well asfinisher 34, the miner then, by hand, guides the drill steel from theformed bore. In prior art designs, before snap-on couplings and hoopsprings, the drill steel was expected to fall downwardly under theinfluence of gravity and the components thereof. The components are thento be assembled within the mine cavern for the next drilling operation.However, due to the rigorous environment of the drilling operation aswell as due to the vagaries of overhead seam structure and the like,such removal of the drill steel assembly is not always effective. Often,off-axis drilling and bending of the components takes place and thevarious portions thereof will not readily slide from the bore. As isapparent, drill steel often is left wedged within the bores and miningaccidents are encouraged with the manual attempts at removal of drillsteel and drill head bits wedged deep within the hole.

[0022] Some drill head body and drill steel middle sections currentlyare connected together by hoop spring clips and snap buttons to reduceloss of drill steel in bores on account of wedging within bores. FIG. 2illustrates an adaptor 58 having a cylindrical bore 48 (FIG. 4), theadaptor has a central section 45 that has an exterior hexagonal size andshape that is identical to the exterior size and shape of the drillsteel 26. The adaptor has an upper male section 46 that has a hexagonalexterior surface as best seen in FIG. 4 that matches and tightly fitsinto the drill head body 54. A lower section 53 of the adaptor tightlyfits into a hexagonal bore of hexagonal drill steel 32. The adaptor isconnected to the drill steel by a hoop spring 51 as is well known andconventional in the art. A bushing seal 56 fits into the upper malesection. In the embodiment illustrated the lower section 53 ishexagonal. Such a hexagonal design is required whenever the drill steel36 is constructed of a plurality of components, as in U.S. Pat. Nos.4,226,290 and 4,632,195.

[0023] The drill head body 54 is connected to the adaptor by a springclip 60 having a button 62. The button 62 is received in a circularopening 55 in the drill head body 54. The adaptor 58 has a groove 49 forattaching the spring clip thereto during assembly. The tail 64 of thespring clip is hooked over the downstream end 47 of the adaptor andpositioned to be received in the groove 49, the button is pushed ontothe adaptor 58 until the button 62 is received in opening 57. Nextbushing seal 56 has a notch 59 that is first aligned with the springclip 60 and is next pushed into the adaptor bore until the bottom wall66 of nipple 68 abuts against the end wall 47 of the adaptor. After thebushing seal 56 has been inserted onto the adaptor the subassembly ofthe bushing seal 56, spring clip 60 and adaptor 58 are inserted intodrill head 54. The subassembly is first aligned so that the button isradially positioned to be in axial alignment with the opening 55in thedrill head. As the subassembly is pushed forward into the drill head thebushing seal and a forward end of the adaptor are positioned within thedrill head body until the button 62 abuts up against the upstream end 44of the drill head. The button can then be manually depressed inward sothat the subassembly (56, 58, 60) can be advanced further inward into areceiving chamber of the drill head body 54. The subassembly (56, 58,60) is then advanced inward into the drill head until button 62 snapsinto opening 55 in the drill head body and drill head upstream end 44simultaneously contact collar 45.

[0024] As best seen in FIG. 2 the drill head body 54 inner chamber has astepped bore forming an annular surface 43. The upstream portion 63ofthe stepped bore has a larger hexagonal cross section and the smallerdownstream portion 61 of the stepped bore is cylindrical. The downstreamcylindrical portion 61 of the chamber transitions into a semisphericalportion. The bushing seal has an intermediate collar 69 positionedbetween the nipple 68 and shank 65 of the bushing seal. The collar 69 isclamped between the annular surface 43 and upstream endwall 47 of theadaptor fixing the bushing seal in position.

[0025] Alternatively, the upstream end wall 44 of the drill head andbutton 62 can be contoured to form cooperating cam surfaces so that asthe adaptor subassembly (56, 58, 60) is pushed inward the button 62 isradially displaced toward the center of the bushing seal 56 bore so thebutton may slide past the upstream end wall into the drill head assemblyuntil it snaps into opening 55. Such cooperating snap buttons are wellknown to ordinary artisans.

[0026] The spring clip can be made from many different types of springsteels, in one exemplary embodiment the spring steel is 0.018×0.255SPRING STEEL, heat treat 44-50 RW “C”. The bushing seal is constructedfrom a flexible material that has good sealing characteristics inpressures at up to 300 psi such as 60 Durometer EPDM.

[0027] The drill head assembly in FIG. 2 has a lower section 53 of theadaptor that is insertable into a hollow drill steel 32, which isconnected to a conventional drive mechanism (not shown) that rotates thedrill steel. A rotary roof bit 30 depicted in FIGS. 4-6 comprises acutting insert 52 mounted in a bit body 54. The insert can be held in arecess in the bit body by any suitable means, such as brazing, frictionfit, etc. Flushing fluid such as water is conducted through outlet s 67in the bit body cools and flushes the insert 52 in the usual manner.

[0028] Water is communicated from inside the drill steel 52 to theoutlets 67 through passages 71(shown in phantom). Although two passages71 are illustrated in the specific embodiment, it should be understoodthat applicants do not intend to limit the scope of the invention toinclude two passages. Applicants contemplate that depending upon theparticular application there may not be a need for any generally axiallyoriented passage or that there may be any number of such passages in thebit body. In a wet drilling operation, the passages would function toprovide a pathway for a flow of fluid (e.g., water) to the forward endof the bit body, i.e., fluid would flow through the passages71.Applicants also contemplate that for a wet drilling operation, theoutside surface of the bit body may contain flats, or some other reliefin the surface, so as to provide a passage for the fluid and debris toexit from near the cutting inserts.

[0029] The primary object of the present drilling methods is to deliverhigh volumes of water to the roof bit inserts to flush away debris andto cool the inserts, particularly at the heat generating cutting edges.Therefore, in the present invention the water pressure has a pressure inthe range of 50 to 300 psi.

[0030] The bushing seal 56 prevents undesirable water pressure lossesthat otherwise might occur due to water leaks between the snap button 62and corresponding opening 57 in the adaptor. The bushing sealadditionally limits water leaking between the downstream end of theadaptor and drill head body.

[0031] In operation, with the drill bit head assembly 34 shown in FIG. 2is snapped into onto the drill steel 32 of a dual boom roof bolter (notshown) or the like. The bolter (and other comparable machines) may beprovided with a variable adjustment for rotational speed, so thisfeature of the method may be preselected and set into the machine inadvance at the optimum or desired rotation within the moderate range ofrpm. When the bore is established, the operator then increases thethrust on the bit up to the maximum preset machine thrust potential. Atthis time the operator also applies full water pressure for delivery tothe bit inserts at dynamic pressures in the range of 50 psi to 300 psi.The supply of water adjacent to the drill bit head during drillingoperations increases the rate of drilling, cools the drill head andassists in suppressing dust. The bushing seal reduces leaks andundesirable pressure losses at the drill head tip that otherwise reducethe efficiency and drilling rate of the roof bit.

[0032] It is now apparent that the objects and advantages of the presentinvention over the prior art have been fully met. Changes andmodifications to the disclosed forms of the invention will becomeapparent to those skilled in the mining tool art.

What is claimed is:
 1. A rotatable drill bit head assembly comprising: adrill head body having an axially forward end and an axially rearwardend, at least one cutting insert at the axially forward end of the drillhead body; the drill head body containing a chamber therein; an adaptorhaving an upper male section and a lower section, and the drill headbody further containing at least one passage at the axially forward endthereof, the at least one passage communicating with the chamber; uponassembling the drill head body and the adaptor, the upper male sectionof the adaptor being received within the chamber of the drill head body,a bushing seal between the adaptor and said drill head body wherein thebushing seal provides a fluid-tight seal between the adaptor and thechamber of said drill head body.
 2. The rotatable cutting bit assemblyof claim 1 wherein the bushing seal includes a shank and a nipple withan intermediate collar positioned between said nipple and shank.
 3. Therotatable cutting bit assembly of claim 2 wherein the chamber includes astepped bore forming an annular surface and said adaptor has an upstreamendwall whereby said collar is clamped between said annular surface andsaid upstream endwall upon assembly of said rotatable cutting bit. 4.The rotatable cutting bit assembly of claim 1 further comprising aspring clip having an integral button, said spring clip is connected tosaid adaptor.
 5. The rotatable cutting bit assembly of claim 4 whereinsaid drill head body has an opening for receiving said button wherebysaid adaptor and said drill head body are snapped together.
 6. Therotatable cutting bit assembly of claim 5 wherein the upper male sectionhas a hexagonal cross-section for forming a tight fit in an upstreamhexagonal portion of said chamber in the drill head body.
 7. Therotatable cutting bit assembly of claim 6 wherein said at least onepassage has an opening adjacent said insert.
 8. A drill steel assemblyfor a drilling machine, said drilling machine having a drill head with achuck for receiving said drill steel assembly, said drill head assemblycomprising: a driver steel component; a finisher drill steel, whereinsaid finisher drill steel is attached to said driver steel component; adrill head body having an axially forward end and an axially rearwardend, at least one cutting insert at the axially forward end of the drillhead body, the drill head body having a fluid chamber therein, the drillhead body further containing at least one passage at the axially forwardend thereof, the at least one passage communicating with the chamber; anadaptor having an upper male section and a lower section, said lowersection of said adaptor tightly fits within said finisher drill steel,and the upper male end of the adaptor being received within the chamberof the drill head body; a bushing seal is positioned between the adaptorand said drill head body wherein the bushing seal provides a fluid-tightseal between the adaptor and the chamber.
 9. The drill steel assembly ofclaim 8 wherein said bushing seal is clamped between said adaptor andsaid drill head body.
 10. The drill steel assembly of claim 9 whereinsaid driver steel, said adaptor and said finisher steel having alongitudinal bore; the passage having an outlet adjacent said cuttinginsert, the outlet of the drill head body being in fluid communicationwith a source of fluid via the chamber of the drill head body and thelongitudinal bore said adaptor, whereby fluid is delivered though saidoutlet to cool said cutting insert and flush debris.
 11. The drill steelassembly of claim 10 wherein said fluid is water.
 12. A drill head bodyfor a wet roof bit comprising: at least one cutting insert at an axiallyforward end of the drill head body; the drill head body containing afluid chamber therein; said chamber having a stepped bore forming anannular surface, the drill head body further containing at least onepassage at the axially forward end thereof, the at least one passagecommunicating with the chamber.
 13. The rotatable cutting bit of claim12 wherein said stepped bore includes an upstream portion having alarger hexagonal cross section and a smaller cylindrical downstreamportion.
 14. The rotatable cutting bit of claim 13 wherein said upstreamportion has an opening therein for receiving a button.
 15. A bushingseal comprising: a shank; a nipple; an intermediate collar between saidshank and said nipple; and a notch formed in said nipple fro receiving aspring clip.
 16. The bushing seal according to claim 15 wherein saidshank and said nipple have a passage therein for communicating fluid.17. The bushing seal according to claim 15 wherein the bushing seal ismade from a flexible material having good sealing characteristics.